1. Field of the Invention
The present invention relates to a resist pattern thickening material, which is applied over a resist pattern and is capable of thickening the resist pattern, and which may form a fine space pattern that exceeds exposure limit of laser beam or light of available exposure devices. The present invention also relates to a process for forming a resist pattern, a semiconductor device, and a process for producing the semiconductor device that utilize the resist pattern thickening material respectively.
2. Description of the Related Art
Currently, semiconductor integrated circuits have been progressed into finer and more precise integration, and LSIs and VLSIs are utilized commercially. Along with these trends, the wiring patterns extend to regions of 200 nm or less, in particular cases extend to regions as low as 100 nm or less. Lithographic technologies are extremely important for forming fine wiring patterns, in which a substrate is coated by a resist film, then is selectively exposed, and then is developed to form a resist pattern. Typically, dry etching is carried out by using resist patterns as a mask, and desired patterns are produced by removing the resist patterns.
In order to improve such wiring patterns utilizing the lithographic technologies, it is necessary to make the light or beam from exposure devices shorter wavelength and also to develop resist materials that are of high resolution and are suitable to the irradiation source. However, in order to make light or beam from an exposure device shorter wavelength, time consuming and expensive researches are required. Further, the developments of new resist materials are not easy that are utilized for exposing light or beam with shorter wavelength.
Accordingly, various technologies have been proposed to form fine resist patterns by means of resist pattern thickening materials in order to form finer patterns.
For example, Japanese Patent Application Laid-Open (JP-A) No. 10-73927 disclose a proposal that forms fine space patterns using KrF (krypton fluoride) excimer laser beam of wavelength 248 nm which is deep ultraviolet light as the exposure light of a resist. In this proposal, resist patterns are formed by exposing a resist of positive resist or negative resist using KrF excimer laser beam of wavelength 248 nm as the exposure light. Thereafter, by means of a water-soluble resin composition, a coated film is provided so as to cover the resist pattern. The coated film and the resist pattern are made to interact at the interface thereof using the residual acid within the material of the resist pattern, and the resist pattern is thickened (hereinafter, the thickening of the resist pattern being sometimes referred to as “swelling”). In this way, the distance between the resist patterns is shortened, and a fine pattern is formed that has the same form as the space pattern.
This proposal makes use of residual acid in the resist pattern to thicken the resist pattern through acid-based reactions, therefore suffers from significant alternation of thickened level due to the environmental conditions such as temperature, alkaline contamination, and other conditions, resulting in hardly controllable thickened level.
JP-A No. 2001-33984 proposes coating basic organic films on negative-type resist patterns that contain acid components, then heating and irradiating. In this proposal, there exist some disadvantages that the resist patterns are limited to negative-type; the process is complicated such that optical irradiation is necessary after the basic organic film is coated; the basic organic film is utilized for no more than making soluble the hydroxy oxide group in phenol compounds in the negative-type resist patterns.
JP-A No. 2002-6512 proposes coating the surface of positive-type resist patterns containing acid components by a first overlay containing acid components and then a second overlay, followed by heating and optical irradiation, thereby making slim the resist pattern without changing the film thickness of the positive-type resist pattern. However, this proposal suffers from the complicated process in that it requires two overlays on the resist pattern.
From the view point to form fine wiring patterns, laser beam having a wave length shorter than 248 nm of KrF excimer laser is desirable such as ArF (argon fluoride) excimer laser having a wave length of 193 nm. On the other hand, pattern formation by means of X-ray, electron beam or the like having a wave length shorter than 193 nm of ArF excimer laser inevitably leads to higher cost and lower productivity, therefore, employment of the ArF excimer laser is desirable.
In the case of fine space pattern formed by resist patterns such as the ArF resist, about a few tens nano meters (nm) is sufficient level to thicken or swell. Thickening over desired level may possibly bring about a desirable result; in some cases, no more than mere improvement as to edge roughness of resist patterns may bring about a sufficient result.
However, in the prior art, the level of thickening or swelling is hardly controllable with respect to resist patters, thus fine patterns are hardly obtainable under delicate controls in general. Further, the prior art typically suffers from significantly unstable thickening or swelling level; the levels of thickening or swelling may be different depending on the irradiating pattern in the prior art; for example, independent rectangular patterns tend to result in larger thickening or swelling level in longer direction than that in shorter direction; hole patterns tend to result in various thickening or swelling levels depending on the pattern density; and/or the level of thickening or swelling often differs depending on the pattern site on a wafer.
Moreover, conventional resist pattern thickening materials are not sufficient in storage stability, there may arise a problem that the thickening level is different depending on the storage period, which cause an undesirable problem in order to apply to processes for producing semiconductors.
Accordingly, an object of the present invention is to provide a resist pattern thickening material that may exhibit superior storage stability and may thicken a resist pattern uniformly, constantly and precisely, without being affected substantially by environmental changes such as temperatures and humidity, and storage period.
Another object of the present invention is to provide a process for forming a resist pattern that is capable to utilize excimer laser beam, the thickening level of the resist pattern is controllable uniformly, constantly and precisely, without being affected substantially by environmental changes such as temperatures and humidity, and storage period, and space pattern of resist may be formed with a fineness exceeding exposure limits or resolution limits of available irradiation sources.
Another object of the present invention is to provide a semiconductor device having a fine wiring pattern that is formed by means of a fine space pattern of resist that is formed by means of the resist pattern thickening material according to the present invention, and a process for producing a semiconductor device adapted to effective mass production of the semiconductor device.